CIDR /39 IPv6 Reference

Large allocation typically used by regional registries or major ISPs

IPv6 uses a 128-bit address space, a massive increase from IPv4's 32 bits. This allows for approximately 340 undecillion (3.4 x 10³⁸) unique addresses, effectively eliminating the address exhaustion concerns of IPv4.

IPv6 addresses are represented as eight groups of four hexadecimal digits, separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). Leading zeros in each group can be omitted, and one sequence of consecutive all-zero groups can be replaced by a double colon (::), for instance 2001:db8::1.

Key Differences from IPv4 Subnetting

• No Broadcast Addresses: IPv6 uses multicast for one-to-many communication instead of broadcast.
• No Network/Broadcast Reserved Addresses: Unlike IPv4, the first and last addresses in an IPv6 subnet are typically usable host addresses. There's no concept of reserving addresses for network ID or broadcast.
• Simplified Addressing: The fixed /64 boundary for host interfaces simplifies network design and enables SLAAC.
• Header Simplicity: The IPv6 header is simpler than IPv4's, which can improve routing efficiency.